Cognitive radio (CR) is a paradigm for wireless communication in which either a network or a wireless node changes its transmission or reception parameters to communicate efficiently while avoiding interfering with licensed users and coexisting with other unlicensed users. This alteration of parameters is based on the active monitoring of several factors in the external and internal radio environment, such as radio frequency spectrum, user behavior and network state. In a CR network, elements of the network may be assigned sensing tasks to maximize the network's responsiveness to the presence of one or more parameters, such as higher priority users, interference, or important changes to the operation of the air interface. Generally, the individual nodes draw conclusions about the spectral occupancy of multiple channels, frequencies, and networks and submit their conclusions to a coordinating node in one or more centralized network or with neighbors in a distributed network. This information is kept within each of the networks.
CR networks in proximity to one another could benefit from a sharing of observations, which would act to extend the effective sensing range and/or reliability of the individual nodes and networks. This would allow networks to better utilize resources and abandon a channel or other frequency spectrum due to the presence of a higher priority user or potential interference. Networks could also discover the extent of their emissions as measured by neighboring networks, thereby allowing them to compare their emissions with expectations and adjust transmit power accordingly.
The prior art describes various types of spectrum sensing systems and methods; however, these systems do not describe how to process this information. For example, the publication to Visotsky et al. entitled “On Collaborative Detection of TV Transmissions in Support of Dynamic Spectrum Sharing” describes combining signal-to-noise (SNR) data for soft combining of sensing, but does not measure parameters such as raw spectrum or time domain measurements that can afford a greater opportunity for extraction of signal information. The publication to Gruenwald entitled “A Power-Aware Technique to Manage Real-Time Database Transactions in Mobile AD-Hoc Networks” describes a repository of information and a reservation system as well as nodes reporting their location information and energy level such as in battery reserves. However, the Gruenwald publication does not describe a database being used to enhance or otherwise coordinate radio operations or make spectrum choices which could improve the capacity and reliability performance of the system. The publication to Grecu et al. entitled “Detection of Anomalous Propagation Echoes in Weather Radar Data using Neural Networks” proposes limiting the examination of a propagation anomaly to an originating node. However, much more information could be gathered by a network of sensing nodes to determine the propagation. Finally, the publication to Kim et al. entitled “WRAN PHP/MAC Proposal for TDD/FDD” describes the use of a separate scanning receiver but does not describe any encrypted transmission of sensing results for protection of the database.
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